Telephone system



\ Jan. 11, 1938. o. l. CARPENTER r AL 2,104,971

TELEPHONE SYSTEM Filed Dec. 2. 1955 5 Sheets-Sheet l Jan. 11, 1938.

o. l. CARPENTER ET Al. 2,104,971

TELEPHONE SYSTEM Filed Dec. 2. 1935 .3 Sheets-SheerI 2 '1h09 i hay /25 g] (9? T 'rbnELnY {'-M 3 CIRCUIT sta 'stal iha l 5f //v /eA/vc/s Mass O. l. CARPENTER ET AL TELEPHONE SYSTEM Jan. 11, 1938. 2,104,971

Filed Dec. 2. 1935 5 Sheets-Sheet 5 ffm goss l5T o d qbooooo" S? 0 3,054- S5 o f 14 Romy 1 l rbi v 5 y Jr-Trai u@ Milam ExcH,

number of the faulty line.

Patented Jan. 11, 1938 UNITED STATES PATENT OFFICE v TELEPHONE SYSTEM England Application December 2, 1935, Serial No. 52,532 In Great Britain December 19, 1934 7 Claims.

The present invention relates to telephone systems and is more particularly concerned with arrangements for detecting faults occurring in automatic or semi-automatic exchanges. It has for its object the provision of means whereby an operator at an attended exchange is informed of the occurrence of a fault at an unattended exchange connected to the one at which the operator is situated.

In such unattended exchanges, a line fault has hitherto been caused, after the lapse of a predetermined period, to lock the aiected line out of use, and release any common exchange appa- Vratus which has been held operated by the fault. This, in the case of an exchange diflicult of access, may mean that the particular subscribers line on which the fault occurs is liable t0 be out of commission for several days.

According to the invention therefore, means are provided in an unattended automatic exchange connected to an attended exchange, whereby on the occurrence of a line or like fault at the former exchange, an operator at the latter exchange is informed, and may ascertain the The operator may also connect to the said faulty line, and apply a tone such as a howler.

In an embodiment of the invention an unattended rural automatic exchange is connected by one or more junctions to an attended or parent exchange. If a line fault at the rural exchange occurs, thefaulty line is isolated from the common exchange apparatus after a predetermined period, the said exchange apparatus being released'. In addition, the faulty line seizes a group of common apparatus connected via a junction to the parent exchange, and the said common apparatus causes a signal to be sent over the junction which informs the operator at the parent exchange' that attention is required.

The operator connects her telephone circuit to the junction and receives a characteristic tone. She now dials a series of ls until the characteristic tone is removed. The total of ls dialled, is

a tone to the said line such as a howler. Disconnection of the operators circuit from the junction leaves the faulty line locked out in such a manner that it cannot again seize the junction and warn the operator until after the fault has been cleared.

In order that the nature of the invention may be better understood, reference should` be made to the accompanying drawings, Figure 1 of which is a subscribers line circuit at an unattended automatic exchange, and Figures 2 and 3 show apparatus for conveyance to an attended exchange of the number of a faulty line. One circuit of the type shown in Figure 1 is provided for each subscriber connected to the automatic exchange, one circuit according to Figure 2 is provided for each 50 such subscribers, and the circuit of Figure 3 is provided one for each unattended exchange. As shown, a maximum of 200 subscribers can be accommodated, but this number may be exceeded by obvious circuit additions and modications.

Reverting to Figure l, the operation of this circuit is of known character. When the subscriber lifts his receiver, a loop is formed from earth on contact bl, over the subscribers line wires, returning to battery via contacts b2, cl, and the coil of relay A, which operates. Contact al removes marking potential derived from contact b3 from the contact banks of the local line finders, and contact a2 applies earth to a start lead ST which initiates the hunting operation of one or more line finders to find the calling line.

When a line finder arrives, an earth potential is extended by it over lead P from the finder circuit to operate relay B, and Contact b3 locks relay B operated to earth on lead P. Contact b4 operates relay C, contact c2 of which extends the earth potential from lead P in the line finder circuit to a corresponding lead inthe final selector multiple, thus marking engaged the calling subscribers line therein.

If the subscriber completes the call correctly, subsequent release of the connection results in release of relays B and C, but if for example, impulsing is not completed, a time delay circuit (not shown) connected to the line finder circuit comes into operation. After a predetermined period, earth is removed from the line finder lead P, allowing relay B to release but holding relay C over the loop. At the same time, an earth is applied, from the line finder circuit over lead 20 to operate the start relay ST in Figure 2 having access to the callers line. Relay ST operates to the lead connected to contact had.

and at contact stl (not shown) disconnects the corresponding ST relay serving the other 50 sub- Y scribers lines in the hundred group in which the calling subscriber is connected. This contact is connected in the second circuit in the position shown by the sil contact in the dotted rectangle in Figure 2 this contact belonging to the complementary ST relay. Contacts h3 and st3 in the other dotted rectangle also belong to the second circuit. Contact st2 connects relays G and H in series whereupon relay H does notroperate, but relay G does. Contact st3 removes the earth connection from the time delay circuit, thus preventing any other line finder circuit from extending earth overv lead 20. Contact gl energizes the switch magnet LF which opens the interrupter contacts Zf. Relay G releases, deenergizing the magnet LF, which releases, moving all its wipers one step forward.

This cycle continues, the relay and magnet interrupting one anothers circuits until wiper LF4 encounters earth applied to lead 5 via contacts b5 and c3 from the line finder circuit over lead M. This potential short-circuits relay G preventing its operation, and operates relay H via contacts st2 and hl. Relay H at contact hl locksV relay H operated via g3, bank LFS, lead c2, to earth at contact b3, at contact h2 operates relays HA and R in series via contact ml, provided that no other HA relays are operated at that time in series with R, at contact h3 prevents restoration of earth to the delay circuit on release of relay ST, and at contact h4 applies earth potential to the line finder circuit over lead Zi, thereby freeing the line nder circuit for use by other subscribers and permitting the release of relay ST. -Relay HA at contact ha! short-circuits the high resistance coil of relay HA (which remains operated) this reduction in resistance preventing the operation of any further I-IA relay in series with relay R, at contacts ha2 and haii applies marking potentials to the wipers LFE and LFS of the switch LF, at contact had prepares to operate relay XA, at contact ha prepares an alternative locking path for relay H, at contact ha applies a marking potential to bank DS2, at contact hall reoperates relay G from earth on contact h5, and at contacts has and hall prepares a path for connecting the operator at the attended exchange to the faulty line.

A delay period is now initiated before the op erator is informed that a fault has occurred. This delay period is controlled by means of earth pulses applied for example at 1 minute intervals The rst of these pulses operates relay XA, and when the pulse is removed, relay XB operates in series over the path:-battery, wil of XA, coil of XB, contacts :ral and r2 to earth. At the end of the next period of l minute, a further earth pulse applied via had holds relay XB operated via contact mbi, and short circuits relay XA Via contact 93172. This relay releases, as also does relay XB at the end of the pulse.

Previous to this, however, contact rc3 operates relay XC which locks operated via contact :co4 to r2. When earth potential is applied for a third time to the hall lead, this potential is now conducted via asbl and :tcl to lead l5 and thence to repeating apparatus of known form which signals the operator at the attended exchange, over a pair of line wires, that a fault has occurred.

Contact :rc3 operates a buzzer relay BZ having a self-interrupting contact bel, this relay, by vibrating its contact, supplying a characteristic tone to the operator via sa! and lead I4.

When the operator replies to the fault signal as by plugging a cord circuit into the end of the line over which the signal has been passed, relay A is operated over lead il by the signalling apparatus at the unattended exchange. This apparatus is of the form of an impulse repeating device, with holding facilities. Relay A at contact al operates relay B which thereupon at contact bl removes an earth potential from various points in bank DSH, at contact b2 removes earth potential from the remaining contacts of this bank, at contact b3 supplies an alternative locking path for relay R, and at contact b4 operates relay RA.

The operator now proceeds to transmit a train of single impulses as for example by dialling a succession of ls by means of a dial or other impulse sending device, counting as she does so. At the commencement of the first impulse, relay A releases, its contact ai energizing relay C and the switch magnet DS in series. Relay B is not released, as it is slugged. At the end of the impulse relay A re-operates, and the switch magnet DS moves the wipers 4DS 1-4 one step forward, though relay C does not release until shortly afterwards. This relay C acts as a guard, its contacts ci and c2 preventing premature operation of certain circuit members at the end of each impulse.

The switch DS is stepped once each time the operator dials an impulse until wiper DSZ reaches the point in its bank marked by contact ha. If the faulty subscribers line is in the rst hundred group, this contact is the second in the bank as shown, if the line is in the second hundred group, then the marking is extended over lead il from another HA relay allocated to this second group to the third contact in the bank.

When the marking is reached by wiper D52, relay SZ operates and at contact sal removes tone from the lead I4 connected to the remote operator, thus indicating from the number of irnpulses dialled, the rst digit of the faulty line, at contact ses connects earth potential to certain of the connected contacts of bank DSI, thus stepping the switch DS by self-interruption at its own contacts ds to contact li, and at contact 324 holds relay SZ operated to contact bil.

To regain the tone in order to ascertain the second number of the faulty line, the operator dials a further single impulse. Relay A releases and 1re-operates as previously described, operating and releasing relay C and stepping the switch l..

DS one step further.

If the next digit of the faulty line is anything other than l, no marking is found by wipermDSZ and relay SZ releases when C operates, its YVccntact ssl re-applying tone to lead l. This is heard by the operator, who continues to transmit single impulses until a further marking in bank DSE is encountered to operate relay SZ a second time. This second marking in bank DSE is derived from the contacts and wiper of bank LF5, the contacts of which bank are commoned or connected together in groups of 10. The switch LF, it will be appreciated, is a 50 point switch and deals with the rst 50 subscribers in a hundreds group; a similar switch connected to the leads lil has access to the last 50 subscribers in the group. As each group of 100 subscribers is served by two switches such as LF, the connection to banks LFE and LF are multipled suitably to the other switches, so that indications may beV lators plug had been removed.

sent to the operator from any of the switches LF.

The second operation of relay SZ, in removing tone from lead I4 informs the operator of the number of the second digit of the faulty line. If this digit had been l, then SZ would have remained operated and the tone would not have been re-applied to lead I4, the operators instructions being such that this would indicate a second digit of l.

When the second digit has been transmitted, the operator continues impulsing, relay SZ being released as before, until wiper DS2 encounters the marking made in the associated bank by wiper LFS. The bank associated with this wiper has'its contacts connected in groups of ten, thus furnishing an indication of the third and last digit of the faulty line. At the end of the third digit, operation of relay SZ followed by release of relay C connects earth from cI via S23 to the larger group of connected contacts of bank DSI, the switch DS stepping its wipers by self-interruption to the first contacts in their banks. Relay SZ remains operated via its contacts S24 to contact bI, so that the operator can now connect a speaking or testing circuit to leads I3 and I4 and thence via sel, S22, DS4, DS3, haS, hall, LF2 and LFI to the faulty line, for the purpose of speakingV or testing this line. When these operations are completed and the plug withdrawn by the operator, relay A releases followed by relays B, R, RA and XC. The latter relay at its contact rc3 discontinues the operation of the buzzer relay BZ and relay HA is released when contact b3 opens its circuit. Relay HA in turn releases relays H and G, and the apparatus is ready for further transmission.

Should the fault on the line circuit be removed whilst the operator is connected to leads I3 and I4, release of relay C (Figure l) cuts the circuit of relay H at contact c2, and this relay and relays HA and R all release. The equipment is then restored to normal as though the oper- If a number of lines become faulty simultaneously, only one fault can be signalled tothe operator at any one time, as only one line finder such as LF can be set into operation at any one time. Again, no fault can be signalled twice to the operator, nor seize a line nder circuit, since if the number of a faulty line has been signalled the faulty line is left with its C relay energized in series over the line Wires via contacts cI, b2 and bl. This condition, however, is unable to apply a marking to lead 5 since the line finder circuit from which earth potential is derived over lead M has been previously stepped offv the faulty circuit when the switch LF reached the faulty line. The line nder cannot again nd the faulty line until after the fault has been removed, as relay A cannot be re-operated and consequently contacts al and a2 cannot affect the line finder.

We claim:

l. In a telephone system, an unattended exchange, a trunk line extending from said exchange to an attended exchange, means in the unattended exchange responsive to a fault on a line in that exchange for transmitting a signal over said trunk line to an operator in the attended exchange, and means controlled over said trunk line by the operator for enabling such operator to ascertain the number of the faulty line.

2. In a telephone system, a first exchange, a

trunk line extending from said exchange to an operators board in a second exchange, means for signalling the operator over said trunk line responsive to a fault on a line in the first exchange, and-means for enabling the operator to ascertain the number of the faulty line, said last means including an arrangement effective while the operator sends trains of impulses over said trunk line for notifying her when the total of impulses in each train corresponds to a digit of the number.

3. In a telephone system, a first exchange, a trunk line extending from said exchange to an operators board at a distant exchange, means cont-rolled from a subscribers line in the rst exchange for signalling the operator over said trunk line, switching mechanism at said first exchange controllable by the operator over said trunk line, and means including a device for transmitting signals over said trunk line while said switching mechanism is being operated for enabling the operator to operate it in accordance with the number of said subscribers line.

4. In a telephone system, a first exchange, a trunk line extending from said first exchange to a second exchange, means in the first exchange responsive to a fault on a line in that exchange for signalling an operator in the second exchange over said trunk line, a step by step switch controlled over said trunk line by the operator to establish connection with the faulty line, and signalling means in the rst exchange cooperating with said switch to notify the operator of the number of the faulty line.

5. In a telephone system, a first exchange, a trunk line extending from a switch in the first exchange to an operators board in a second exchange, a finder in the first exchange responsive to an unstandard condition on a line to find such line, means including said nder for marking the bank of said switch in accordance with the number of the line having the unstandard condition, and signalling means in the first exchange for enabling the operator to control said switch in accordance with said marking, to thereby ascertain the number of the line having the unstandard condition.

6. In a telephone system, a rst exchange, a finder in said exchange responsive to an unstandard condition on a line to find such line, a trunk line extending to an operators board in a distant exchange, means responsive to the operation of said finder for signalling the operator over said trunk line, and a switch controlled by the operator over said trunk line to connect the same with said finder and through the finder to the line having the unstandard condition.

7. In a telephone system, an exchange including a subscribers line, said line having a lockout relay, means including said relay responsive to a prolonged calling condition on said line to lock out the line and terminate the calling condition in so far as it affects the switching equipment for extending the line, means responsive to such lock out for signalling an operator in a distant exchange, and means including switching equipment in the first exchange controlled by the operator for advising the operator of the number of the locked out line.

OLIVER IRVING CARPENTER. BENJAMIN FRANCIS MOSS. 

